As shown in FIGS. 1, 2, two conventional solid tires are illustrated. The prior art solid tire of the FIG. 1 is produced by placing raw rubber layer by layer on top of the other in a tire molding device and then is heated and pressed into shape.
Such a prior art solid tire has the following disadvantages:
1. The cross section of the solid tire is too large to be processed readily, and it is easily deformed in processing and it is relatively heavy in weight. PA1 2. The solid tire made of hard rubber material is not good of absorbing shocks when used on bumpy roads, so it results in damage to the structure of a vehicle and the tire cracks after a long period of use. It is not comfortable and safe in use. PA1 1. The foaming process (addition of sulphur in the secondary processing) results in the aging of the outer tire 10 whose strength and resistance to wear are reduced accordingly, i.e. the operational life span is shortened. PA1 2. Such a foamed inner tire portion can not stand heavy load, so the use of this solid tire is limited. PA1 3. The foamed tire portion is easily deformed and peeled off, resulting in the shift of center gravity of the solid tire during rotation. This can cause driving hazards.
The second prior art solid tire (shown in FIG. 2) has an inner portion made of foamed rubber. It is made by firstly placing a rubber material and a foaming agent in an outer tire 10 and the mixture is subject to high temperature and pressure to form a foamed layer 20 adhered to the inner side of the outer tire 10.
Such a prior art solid tire with foamed inner portion has the following disadvantages in practical use: